Apex domains cannot have CNAME records.
Question and response
Question
dig dnsever.net. NS
Answer
dnsever.net. 5 NS ns4.dnsever.net.
dnsever.net. 5 NS ns4.dnsever.org.
dnsever.net. 5 NS ns4.dnsever.co.kr.
dnsever.net. 5 NS ns4.dnsever.co.uk.
dnsever.net. 5 NS ns4.dnsever.com.
Authority
The response has no authority records.
Additional
ns4.dnsever.net. 5 A 91.134.148.194
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0